|
 John Dalton | Well known for his publication on the Atomic Theory in 1803 |
| Atom | The smallest unit of an element that maintains the properties of that element |
| Nucleus | An atom's central region, which is made up of protons and neutrons |
| Electron | A subatomic particle that has a negative charge |
| Electron cloud | A region around the nucleus of an atom where electrons are likely to be found |
| Neutron | A subatomic particle that has no charge and that is found in the nucleus of an atom |
| Proton | A subatomic particle that has a positive charge and that is found in the nucleus of an atom |
| Atomic Mass Unit (AMU) | The SI unit that describes the mass of an atom or its particles |
| Atomic Number | The number of protons in the nucleus of an atom |
| Isotope | An atom of an element that has a different number of neutrons than other atoms of the same element |
| Mass Number | The sum of the number of protons and neutrons in the nucleus of an atom |
| Atomic Mass | The weighted average of the masses of all the isotopes of an element and expressed in AMU's |